ML20202E003

Responds to NRC Re Deviation Noted in Insp Rept 50-312/86-07.Corrective Actions:Insulation of Two Turbine Bypass Valve Shielding Wires Will Be Reworked During Current Shutdown by 860731

ML20202E003
Person / Time
Site:	Rancho Seco
Issue date:	06/13/1986
From:	Julie Ward SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
Shared Package
ML20202D996	List: IR 05000312/1986007 ML20202E003
References
JEW-86-108, NUDOCS 8607140264
Download: ML20202E003 (4)

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SACRAMENTO MUNICIPAL UTILITY DISTRICT O 6201 S Street. PO. Box 15830, sacramento CA 95852-1830,(916) 452-3211 AN ELECTRIC SYSTc.M SERVING TH6HESRT OF CALIFORNIA l.n ,.,

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JEW 86-108 -

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June 13, 1986 J B MARTIN REGIONAL ADMINISTRATOR REGION V 0FFICE OF INSPECTION & ENFORCEMENT U S NUCLEAR REGULATORY COMMISSION 1450 MARIA LANE SUITE 210 WALNUT CREEK CA 94596 DOCKET NO. 50-312 LICENSE NO. DPR-54 NOTICE OF DEVIATION FROM NRC INSPECTION 86-07, UNINSULATED SHIELD DRAIN WIRES The Sacramento Municipal Utility District hereby submits the response to the subject Notice of Deviation in accordance with 10 CFR 2.201.

If there are any questions concerning this response, please contact Mr. Ron Colombo at the Rancho Seco Nuclear Generating Station.

Ju E. WARD ASSISTANT GENERAL MANAGER, NUCLEAR (ACTING) 1 8607140264 860708 PDR ADOCK 05000312 l

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l DISTRICT RESPONSE TO NRC INSPECTION 86-07 NOTICE OF DEVIATION As a result of the inspection conducted by Mr. A. Hon between February 21 and April 11, 1986, the following alleged deviation from accepted standards was identified:

Rancho Seco Nuclear Generating Station Updated Safety Analysis Report (USAR) Chapter 10, Steam and Power Conversion System, Paragraph 10.1, Design Bases, states that:

"The Steam bypass-valves to the condenser, atmospheric dump valves and main-steam valves are used, as necessary, follow-ing loss of external load and subsequent turbine and reactor trip."

In addition, USAR Chapter 7, Instrumentation and Controls, Paragraph 7.2.3, Integrated Control System, Paragraph 7.2.3.1, Design Bases, states that:

"The combined actions of the control system, the turbine by-pass to the condenser, and the atmosphic dump valves permit a 50 percent load rejection without safety valve operation."

SMUD Contruction Specification NEPM 5304.8C, effective 1/1/86, Section 5.9.3 Instrumentation and Control, which applies to these systems, states that:

"A bare shield drain wire shall be insulated with Kynar heat shrinkable tubing if the wire can possibly come in contact with other uninsulated wire, metal components, or metal devices.

Unterminated shield drain wires (i.e. " floating" shield) shall be insulated with a Kynar heat shrinkable end cap."

Contrary to the above commitments, an unterminated shield drain wire was left uninsulated and in contact with the metal container for the follow-ing field terminations:

Turbine Bypass Valves E/P transducers nos. PY-20561, PY-20563 and PY-20566.

Atmospheric Dump Valves E/P transducer no. PY-20571 This condition, if left uncorrected, could potentially degrade the signal quality for the circuits by introducing multiple group points.

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Response

The District acknowledges the non-conforming condition of control shield drain wires being left uninsulated for 2 of the Turbine Bypass Valves.

This non-conformance is however a non-conformance with current shielding practices and not practices which were accepted as being typical when the plant was being constructed. It should be noted that for the Atmo-spheric Dump Valves, each shield lead was insulated as documented in the disposition of NCR 5507 Rev. O, dated April 14, 1986.

Of the 3 identified discrepancies for-the Turbine Bypass Valves, only 2 were actually determined to have uninsulated shield drain wires. These 2 discrepancies (PY-20561 and PY-20566) were dispositioned to be rework-ed on May 9, 1986, in accordance with NCR 5512 Rev. O, dated April 16, 1986.

The District recognizes the importance of ensuring the functional capa-bility of the Turbine Bypass and Atmospheric Dump Valves, as described in the Updated Safety Analysis Report, however, the significance of this Notice of Deviation can best be understood recognizing the voltage levels which are used in the control of these valves.

The control signal is -10 volts to +10 volts which is significantly larger than normally encountered noise in similar circuits even where ground loops of the shielding are encountered. There is no operational history of the shield preparation causing improper valve operation over the life of the plant. The lack of insulation on the 2 Turbine Bypass Valve's shielding wires will be reworked during the current shutdown by July 31, 1986.

In order to develop a higher level of confidence for systems which may use lower control voltages and which are therefore more susceptable to shield ground loop interference, Nuclear Engineering will either develop a sample inspection program or will analytically demonstrate that shield ground loop interference is not a concern.

The sample inspection would consist of a comprehensive listing of elec-trical panels, equipment and devices which have been determined to be important to plant safety and operation. This listing would be checked against the cable, Raceway and Tracking Report to establish which equip-ment utilize cables with a shield. This group would be considered the Rancho Seco population which could be affected by a similar failure to properly terminate cable shields. From this group a random sample would be selected, which when inspected and found to be correctly terminated, would provide a 99.9% assurance that the same results exist in the balance of the sample population. Should this confidence level not be achieved, a full plant inspection and rework of the defined population would be undertaken. The sample inspection program would be initiated by July 1, 1986 and any additional discrepancies would be identified prior to plant restart. The resulting rework schedule (if any) would be developed on a case-by-case basis.

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i l The analysis would demonstrate that, with the extensive ground grid

! system at Rancho Seco, the path of least resistance for a ground loop is not through any shield wires and therefore the identified discrep-ancy is not a genuine technical concern and that no further inspection i .and rework is necessary. Future work will be>in accordance with cur-rent standards.

A decision as to which approach will be used in the resolution of this issue will be made by July 1, 1986.

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